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Assessing Undiscovered Resources of the Barnett-Paleozoic Total Petroleum System, Bend Arch–Fort Worth Basin Province, Texas*
By
Richard M. Pollastro1, Ronald J. Hill1, Daniel M. Jarvie2, and Mitchell E. Henry1
Search and Discovery Article #10034 (2003)
*Online adaptation of presentation at AAPG Southwest Section Meeting, Fort Worth, TX, March, 2003 (www.southwestsection.org)
1U.S. Geological Survey, Denver, CO
2Humble Geochemical Services, Humble, TX
Abstract
Organic-rich Barnett Shale
(Mississippian-Pennsylvanian) is the primary source rock for oil and 
gas
that is
produced from Paleozoic reservoir rocks in the Bend Arch–Fort Worth Basin
Province. Areal distribution and geochemical typing of hydrocarbons in this
mature petroleum province indicates generation and expulsion from the Barnett at
a depocenter coincident with a paleoaxis of the Fort Worth Basin.
Barnett-sourced hydrocarbons migrated westward into reservoir rocks of the Bend
Arch and Eastern shelf; however, some oil and gas was possibly sourced by a
composite Woodford-Barnett total petroleum system of the Midland Basin from the
west.
Current U.S. Geological assessments
of undiscovered oil and gas are performed using the total petroleum system (TPS)
concept. The TPS is composed of mature source rock, known accumulations, and
area(s) of undiscovered hydrocarbon potential. The TPS is subdivided into
assessment units based on similar geologic characteristics, accumulation type
(conventional or continuous), and hydrocarbon type (oil and (or) gas).
Assessment of the
Barnett-Paleozoic TPS focuses on the continuous (unconventional) Barnett
accumulation where gas and some oil are produced from organic-rich siliceous
shale in the northeast portion of the Fort Worth Basin. Assessment units are
also identified for mature conventional plays in Paleozoic carbonate and clastic
reservoir rocks, such as the Chappel Limestone pinnacle reefs and Bend Group
conglomerate, respectively. However, Barnett continuous gas is expected to add
the greatest volume of undiscovered, technically recoverable resource.
Undiscovered Barnett Shale gas will be assessed after mapping “sweet spots” and
outlying areas of hydrocarbon potential, and by defining distributions of
drainage (cell) size and cell estimated ultimate recovery. An example of a
Barnett “sweet spot” is the Greater Newark East area where thick, siliceous
Barnett has reached the gas window, and is overlain and underlain by impermeable
limestones that contain fractures that are induced during completion.
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Introduction and BackgroundOil and
Continuous-type accumulations include fractured shale and fractured
chalk oil and
Subsequent to the 1995 USGS
Assessment, Schmoker and others (1996) and Kuskraa and others (1998)
estimated undiscovered (also referred to as undeveloped), technically
recoverable Current
USGS assessments incorporate the total petroleum systems–assessment unit
(TPS-AU) method (Klett et al., 2000; Magoon and Schmoker, 2000) to
estimate undiscovered oil and
Petroleum geochemistry studies by Jarvie and others (2001), Jarvie and
Claxton (2002), and in this report indicates that the organic-rich
Barnett Shale is the primary source rock for oil and
Province Boundary, Structural Elements, and Tectonic HistoryThe boundary of USGS Province 045, Bend Arch-Fort Worth Basin, is defined by State and county lines that closely follow U.S. Congressional Districts, rather than by geologic elements. However, the Province boundary generally follows the Ouachita structural front to the east and southeast, the Llano Uplift to the south, and the Texas-Oklahoma State line (the Red River) to the north (Figure 3). The western boundary trends north-south along county lines that define the junction with the Permian Basin Province (USGS Province 044) where part of the eastern shelf of the Permian Basin is included in the Bend Arch-Fort Worth Basin Province (Figure 3).
Major structural features of
USGS Province 045 include the Muenster and Red River Arches to the
north, and the Bend and Lompasas Arches along the central part of the
Province. Along the eastern portion of the province is an area that
includes the Eastern and Chappel Shelves and Concho Arch, collectively
also known as the Concho Platform (Figure 3). The Mineral Wells fault
runs northeast-southwest through Palo Pinto, Parker, Wise, Denton
Counties and joins with the Newark East fault system. The fault system
bisects the Newark East Field to create a zone of poor production in
Barnett Shale The evolution of the Fort Worth Basin and Bend Arch structures are critical to understanding burial histories and hydrocarbon generation of the Barnett-Paleozoic TPS. The asymmetrical, wedge-shaped Fort Worth Basin is a peripheral Paleozoic foreland basin with about 12,000 ft of strata preserved in its deepest northeast portion and adjacent to the Muenster Arch and Ouachita structural belt; the approximate location of its present-day axis is shown in Figure 3. The basin is similar to other basins of the Ouachita structural belt, such as the Black Warrior, Arkoma, Val Verde, and Marfa Basins that formed in front of the advancing Ouachita structural belt as it was thrust onto the margin of North America. Thrusting occurred during a late Paleozoic (Late Mississippian and Early Pennsylvanian time) episode of plate convergence (Flippen, 1982).
The Bend Arch extends
northward from the Llano Uplift; it is a broad subsurface,
north-plunging, positive structure. The arch formed as a hingeline by
(1) down-warping of its eastern flank due to subsidence of the Fort
Worth Basin during early stages of
General Stratigraphy and Petroleum Production history
The stratigraphic section of
the Bend Arch–Fort Worth Basin Province is generalized in
Figure 4.
Producing intervals, vertical distribution of total petroleum system
elements, and proposed assessment units for the Barnett-Paleozoic TPS
are also shown in Figure 4. Oil and The sedimentary section in the Fort Worth Basin is underlain by Precambrian granite and diorite. Cambrian rocks include granite conglomerate, sandstones, and shale that are overlain by marine carbonate rocks and shale (Flippen, 1982). No production has been reported from Cambrian rocks. The Silurian, Devonian, Permian, Jurassic, and Triassic are absent in the Fort Worth Basin (Flippen, 1982).
From Cambrian to
Mississippian time, the area that is now the Fort Worth Basin was part
of a stable cratonic shelf with deposition dominated by carbonates
(Burgess, 1976). Ellenburger Group carbonate rocks represent a broad
epeiric carbonate platform that covered virtually all of Texas during
the Early Ordovician. A pronounced drop in sea level at the end of
Ellenburger deposition resulted in prolonged platform exposure and
The Barnett Shale was
deposited over the resulting unconformity. Provenance of the
terrigenous material that constitutes the Barnett Shale was from Ouchita
thrust sheets and the reactivation of older structures such as the
Muenster Arch. Clastic rocks of similar provenance dominate the
Pennsylvanian part of the stratigraphic section in the Bend Arch-Forth
Worth Basin. With progressive subsidence of the basin during the
Pennsylvanian, the western basin hinge line and carbonate shelf,
represented by carbonate rocks of the Comyn, Marble Falls, Big Saline,
and Caddo Formations, continued to migrate westward. Deposition of the
thick basinal clastic rocks of the Atoka, Strawn, and Canyon Formations
occurred at this time (Walper, 1982). These Middle and Late
Pennsylvanian age rocks consist mostly of sandstones and conglomerates
with fewer and thinner limestone beds (Figure 4). Wolfcampian age
sandstones also produce oil and
Shows of oil and
Cumulative production in USGS
Province 045 from conventional reservoirs prior to the 1995 USGS
Assessment was about 2 billion barrels of oil (BBO) and 7 trillion cubic
feet of Barnett-Paleozoic Total Petroleum System
Oil and Source Rock, Thermal Maturity, and Hydrocarbon Generation The primary source rock of the Bend Arch-Fort Worth Basin is the Mississippian-Pennsylvanian Barnett Shale. The Barnett Shale commonly exhibits high gamma-ray log response at the base of the unit (or basal “hot shale”). Other potential source rocks of secondary importance (Figure 4) are of Early Pennsylvanian age and include (1) dark fine-grained carbonate rock and shale units within the Marble Falls Limestone, (2) black shale facies of the Smithwick Shale (Walper, 1982; Grayson et al., 1991), and (3) several thin Pennsylvanian age coal beds in Wise, Jack, Young, Parker, Palo Pinto, and McCulloch Counties (Mapel et al., 1979). The Barnett Shale source rock was deposited over a large part of North-Central Texas; however, because of post-depositional erosion the present distribution of the Barnett is limited to the Bend Arch-Forth Worth Basin Province (Maple et al., 1979). The Barnett Shale is more than 1,000 ft thick along the southwest flank of the Muenster Arch (Maple et al., 1979; Henry, 1982). The Barnett Shale is present within the Midland, Delaware, and Palo Duro Basins to the west and the Hardeman Basin to the north (Figure 3). A smaller Barnett total petroleum system is probably present in the Hardeman Basin to the north (Figure 3). The Barnett Shale is eroded in areas (1) along the Red River-Electra and Muenster Arches to the north, (2) along the Llano uplift to the south where it outcrops, and (3) along the easternmost portion of USGS Province 045 where the Barnett laps onto the Eastern Shelf-Concho Platform (Figure 3). Small isolated remnants of Barnett Shale have been identified on the unconformity surface of the Ordovician Ellenburger Group carbonate rocks in the western most part of the USGS Province 045). The Barnett is absent in the Sherman Basin to the northeast, and absent east of the Ouachita Thrust Belt (Figure 3). Average total organic carbon (TOC) content in the Barnett Shale is about 4% (by weight) and TOC is as high as about 12% in samples from outcrops along the Llano uplift on the south flank of the Fort Worth Basin (Henk et al., 2000; Jarvie et al., 2001). The highest average TOC for the Barnett Shale appears to follow a depocenter that is coincident with a paleo-axis of the Fort Worth Basin (Figure 3).
The Barnett Shale has
geochemical characteristics similar to other Devonian-Mississippian
black shales found elsewhere in the U. S. (e.g., Woodford, Bakken, New
Albany, and Chattanooga Formations). These black shales all contain
oil-prone organic matter (Type II kerogen) based on hydrogen indices
greater than 350milligrams of hydrocarbons per gram of TOC and generate
a similar type of high quality oil (low sulfur, >30 API gravity). Oils
found in the far western and northern portions of USGS Province 50 are
all typed as Barnett-sourced oils. Although decomposition of kerogen
cracking is a source of oil and Low
levels of maturation in the Barnett Shale at vitrinite reflectance (Ro),
estimated at 0.6-0.7%, yields oils of 38o API gravity in
Brown County. The oils found in Shackelford, Throckmorton, and Callahan
Counties as well, as in Montague County (Figure 3), are derived from the
Barnett Shale at the middle of the zone of oil generation (oil window)
thermal maturities levels (about 0.9% Ro). Although
condensate is associated with
Thermal maturity of Barnett
Shale can also be derived from TOC and Rock-Eval (Tmax )
measurements. Although Tmax is not very reliable for high
maturity kerogens due to poor pyrolysis peak yields and peak shape, the
extent of kerogen transformation can be utilized. For example, Barnett
Shale having a 4.5% TOC and a hydrogen index of less than 100 is in the
wet or dry Little or no data are available on the variability of the Barnett Shale organic matter content and type outside of Newark East Field (Figure 6). Average values for low maturity Barnett Shale (Tmax < 435oC) are about 3.26% TOC using well cuttings. This same set of samples has initial hydrocarbon potentials of about 172 barrels of oil per acre feet (BO/AF), which are dramatically lower than expected for the Barnett Shale. This is probably due to a mixing of terrestrial plant organic matter on the edges of the basin with marine organic matter common to the Barnett.
In contrast, low maturity
Barnett Shale from outcrops in Lampasas County have initial TOC values
averaging about 12% with hydrocarbon potentials averaging 1035 BO/AF. A
good average value for the Barnett Shale is derived from the Mitcham #1
well in Brown County in which TOC is measured at 4.2% and the
hydrocarbon potential is 354 BO/AF. Using these data we can determine
that the TOC values will decrease 36% during maturation from the
immature stage to the This study found a poor correlation between measured Ro and present-day burial depth for the Barnett Shale, as did Bowker (2002). Vitrinite iso-reflectance contours commonly cross-cut both basin structure and structure contours on the top of the Barnett Shale. Similarly, samples of Barnett Shale in the deepest part of the Fort Worth Basin along the southwest flank of the Muenster Arch in Denton County, record lower Ro than the shales at shallower depths to the east and in Newark East Field. Also, north of Lampasas County, rock samples along the Ouchita thrust front have higher Ro than those from greater present-day depths. Thus in many areas of the Bent Arch-Fort Worth Basin Province, thermal maturity of the Barnett Shale determined from Ro appears to be influenced strongly by heat-flow regimes generated from Ouchita thrusting.
The Barnett Shale is
thermally mature for hydrocarbon generation over most of its area within
USGS Province 045 (Figure 3). The Barnett source rock is presently in
the oil-generation window along the north and west parts of the
province, and in the
In the main
Reservoir rocks of the Barnett-Paleozoic TPS include both clastic and carbonate rocks ranging in age from Ordovician to Early Permian (Wolfcampian); they are listed in the stratigraphic section and total petroleum system distribution chart of Figure 4. Most production from conventional reservoirs is from rocks of Pennsylvanian age, whereas the only recognized production from an unconventional (continuous) accumulation is from the Mississippian-Pennsylvanian fractured Barnett Shale. Conglomerate of the Pennsylvanian Bend Group is the main producing reservoir at giant Boonsville Field of Wise and Jack Counties with cumulative production through 2001 of more than 3 TCFG (Swindell, 2002). Jarvie and others (2001) reported that oil sourced from the Barnett Shale is produced from numerous reservoir rocks in the Bend Arch-Fort Worth Basin, including Barnett Shale, Caddo Formation, Canyon Group, Chappel Limestone, Bend Group,and Ellenburger Group (Figure 4). Additional reservoir rocks of the Barnett-Paleozoic TPS considered in this report are in the Viola Limestone, Marble Falls Limestone, Atoka Formation, Strawn Group, and Cisco Group (Figure 4). Historical production summaries for many of these reservoirs are given in Ball and Perry (1996). Seal rocks in the Barnett-Paleozoic TPS are mostly shale units and dense, low permeability carbonate rock (Figure 4) that are distributed on both regional and local scales. The Barnett Shale is a major regional seal for older reservoirs, mostly porous carbonate rock reservoirs of the Ellenburger Group. Production from the Barnett Shale is largely dependent on the presence or absence of Marble Falls and Viola limestones (Figure 4). Although these formations are not considered seal rocks in areas where they are tight and not water wet, they serve as barriers (Figure 6) to confine hydraulic-induced fracturing (referred to as frac barriers) and help retain formation pressures during well stimulation (Bowker, 2002; Shirley, 2002). Traps for conventional hydrcocarbon accumulations are mostly stratigraphic for carbonate rock reservoirs and both structural and stratigraphic in clastic-rock reservoirs. Combination structural and stratigraphic traps are also common in Pennsylvanian sandstone reservoirs. Stratigraphic traps in carbonate rocks result from (1) a combination of facies and depositional topography, (2) erosion, (3) updip pinchout of facies, and (4) diagenetically controlled enhanced-permeability and porosity zones. A good example of a carbonate stratigraphic trap is the pinnacle reef traps of the Chappel Limestone (Figure 4), in which local porous grainstone and packstone are restricted to isolated buildups or reef clusters on low-relief paleotopography of the eroded Ellenburger Group. Chappel pinnacle reefs are draped and sealed by the overlying Barnett Shale. Stratigraphic traps in Atoka Formation sandstones and conglomerates are mainly pinch outs related to facies changes or erosional truncation. Structural traps for Pennsylvanian-age sandstones and conglomerate reservoir rocks are mainly simple anticlines and fault-bounded anticlines. Proposed Assessment Units for the Barnett-Paleozoic TPS
The USGS assesses
conventional accumulations using distributions of size and number of oil
and
Continuous accumulations
commonly cover large geographic areas. Thus, multiple assessment units
are commonly defined for a particular continuous accumulation, such as
the Barnett Shale, which commonly are based on differences primarily
with regard to (1) geologic facies, thickness, structure; (2)
hydrocarbon type; (3) organic geochemistry; (4) thermal maturation (oil-
and
Fractured Barnett Shale Continuous Oil and
Oil and The main producing facies of the Barnett is a black, organic-rich siliceous shale with a mean composition, by weight, of about 45% quartz, 27% clay (mostly illite/smectite, and illite), 10% carbonate (calcite, dolomite, and siderite), 5% feldspar, 5% pyrite, and 5% TOC (Lancaster et al., 1993; Henk et al., 2000; Bowker, 2002). Average porosity in the productive portions of the Barnett is about 6% and matrix permeability is measured in nanodarcies (Lancaster et al., 1993; Bowker, 2002).
The lithology and
petrophysical characteristics of units above and below the Barnett Shale
are critical to
A minimum of three assessment
units (Table 1) is proposed for the Barnett Shale continuous
accumulations, each with different geologic and production
characteristics: (1) a Newark East Field
The siliceous nature of the
Barnett Shale, and its relation to fracture enhancement in the area of
Newark East Field, has been noted by Lancaster et al. (1993) and Henk
and others (2000). Thus, the geographic extent of the organic-rich
siliceous facies of the Barnett Shale is of particular interest in this
study for defining sweet spots. Also, the second assessment unit, where
the Barnett Shale subcrop is Ellenburger Group carbonate rocks, is
currently being tested by several operators. The resource potential of
this unit will be guided, in part, by the near-future results of current
testing with directional wells and various completion methods to
determine optimum completion techniques for
Historically, typical EURs
for Barnett
A Barnett-Paleozoic Total
Petroleum System has been defined for the Bend Arch-Fort Worth Basin
Province, USGS Province 045. Distribution and geochemical typing of
hydrocarbons produced from Paleozoic reservoirs rocks indicate
generation, expulsion and emplacement from the organic-rich,
Mississippian-Pennsylvanian Barnett Shale. Reservoir rocks of the
Barnett-Paleozoic TPS are carbonate and clastic rocks that range in age
from Ordovician to Permian (Wolfcampian). Reservoirs are sealed by
thick shale or dense, impermeable carbonate rocks. The boundaries for
the Barnett-Paleozoic TPS are major geologic structures to the north,
south, and east. However, the western boundary of the Barnett-Paleozoic
TPS is poorly defined, and therefore only tentative at this time. The
western Barnett-Paleozoic TPS boundary splits the area of the Eastern
Shelf and Concho Platform where reservoir rocks containing
Barnett-sourced hydrocarbons are likely mixed with hydrocarbons
generated from source rocks of the Midland Basin to the west. Further
oil and
TOC content in the Barnett
Shale averages 4% and consists of oil-prone Type II kerogen. Oils were
initially generated from the decomposition of organic matter in the
Barnett Shale at low levels of thermal maturities, whereas
Preliminary analysis of the
Bend Arch-Fort Worth Basin Province has identified five conventional and
three continuous assessment units for assessing undiscovered,
technically recoverable resources of the Barnett-Paleozoic TPS. The
three continuous assessment units are areas of potential Barnett Shale
production that are defined by both geologic conditions and geochemical
and thermal maturity parameters. The greatest volume of undiscovered
resource in the Barnett-Paleozoic TPS is expected from continuous Allard, J., 2000, Barnett Shale play hot in North Texas: Landman, p. 26-28, Accessed June 2002 at URL http://www.landmand.org.
Ball M. M.,
and W. J. Perry, 1996, Bend Arch-Fort Worth Basin Province (045), in D.
L. Gautier, G. L. Dolton, K. I. Takahashi, and K. L. Varnes, eds., 1995
National assessment of United States oil and
Bowker, K.,
2002, Recent developments of the Barnett Shale play, Fort Worth Basin,
in Law, B.E. and Wilson, M., eds., Innovative Comer, J. B, 1991, Stratigraphic analysis of the Upper Devonian Woodford Formation, Permian Basin, West Texas and Southeastern New Mexico: Texas Bureau of Economic Geology Report of Investigations 201, 63 p. Devon Energy Corporation, 2002, Mid-year company operations update and Barnett Shale school, June 20, 2002: Accessed August 2002 at URL www.dvn.com. Flippin, J. W., 1982, The stratigraphy, structure, and economic aspects of the Paleozoic strata in Erath County, North-Central Texas, in C. A. Martin, ed., Petroleum geology of the Fort Worth Basin and Bend Arch area: Dallas Geological Society, p. 129-155.
Gautier, D.
L., G. L. Dolton, K. I. Takahashi, and K. L. Varnes, K. L., eds., 1996,
1995 National assessment of United States oil and Grayson, R. C. and G. K. Merrill, eds., 1991, Carboniferous geology and tectonic history of the Southern Fort Worth (Foreland) Basin and Concho Platform, Texas: AAPG, 1991 Annual Convention, Dallas Geological Society Guidebook, Field Trip No. 13, 67 p. Grayson, R. C., Jr., G. K. Merrill, L. L. Lambert, and M. J. Pranter, 1991, Carboniferous geology and tectonic history of the southern Fort Worth (foreland) Basin and Concho Platform, in R. C. Grayson and G. K. Merrill, eds., Carboniferous geology and tectonic history of the Southern Fort Worth (foreland) Basin and Concho Platform, Texas: AAPG, 1991 Annual Convention, Dallas Geological Society Guidebook, Field Trip No. 13, p. 3-67. Hall, J., 2002, Barnett Shale geology, in Devon Energy Corporation, Mid-year operations update and Barnett Shale school, June 20, 2002: Accessed August 2002 at URL www.dvn.com. Henk, F., J. Breyer, and D. M. Jarvie, 2000, Lithofacies, petrology, and geochemistry of the Barnett Shale in conventional core and Barnett Shale outcrop geochemistry [abs], in L. Brogden, ed., Barnett Shale Symposium, Fort Worth Texas, Oil Information Library of Fort Worth, Texas, p. 7.
Jarvie, D. M.,
B. L. Claxton, F. Henk, and J. T. Breyer, 2001, Oil and shale
Jarvie, D. M.,
and B. L. Claxton, 2002, Barnett Shale oil and Kerans, C., 1988, Karst-controlled reservoir heterogeneity in Ellenburger Group carbonates of West Texas: AAPG Bulletin, v. 7, p. 1160-1183. Klett, T. R., J. W. Schmoker, and T. S. Ahlbrandt, 2000, Assessment hierarchy and initial province ranking, Chapter AR, in U.S. Geological Survey World Energy Assessment Team, U.S. Geological Survey World Petroleum Assessment 2000 – Description and results, USGS Digital Data Series DDS-60, Version 1.0, CD-ROM, Disk one, 31 p.
Kuuskraa, V.
A., G. Koperna, J. W. Schmoker, and J. C. Quinn, 1998, Barnett Shale
rising star in Fort Worth Basin: Oil and
Lancaster, D.
E., S. McKettta, and P. H. Lowry, 1993, Research findings help
characterize Fort Worth Basin’s Barnett Shale: Oil and Magoon, L. B., and W. G. Dow, 1994, The petroleum system, in L. B. Magoon, and W. G. Dow, eds., The Petroleum system – From source to trap: AAPG Memoir 60, p. 3-24. Magoon, L. B., and J. W. Schmoker, 2000, The total petroleum system – The natural fluid network that constrains the assessment unit, Chapter PS, in U.S. Geological Survey World Energy Assessment Team, U.S. Geological Survey World Petroleum Assessment 2000 – Description and results, USGS Digital Data Series DDS-60, Version 1.0, CD-ROM, Disk one, 31 p. Mapel, W. J., R. B. Johnson, G. O. Bachman, and K. L. Varnes, 1979, Southern Mid-Continent and southern Rocky Mountains Region, in L. C. Craig, and W. C. Connor, eds., Paleotectonic investigations of the Mississippian System in the United States: Part 1 – Introduction and regional analyses of the Mississippian System: U.S. Geological Survey Professional Paper 1010, p. 161-187.
Reeves, S.,
2002,
Schenk, C. J.,
and R. M. Pollastro, 2001, Natural
Schmoker, J.
W., 1996, Method for assessing continous-type (unconventional)
hydrocarbon accumulations, in D. L. Gautier, G. L. Dolton, K. I.
Takahashi, and K. L. Varnes, eds., 1996, 1995 National assessment of
United States oil and
Schmoker, J.
W., C. J. Quinn, R. A. Crovelli, V.F. Nuccio, and T. C. Hester, 1996,
Production characteristics and resource assessment of the Barnett Shale
continuous (unconventional) Shirley, K., 2002, Barnett Shale living up to potential: AAPG Explorer, v. 23, no. 7, p.18-27. Sloss, L. L., 1976, Areas and volumes of cratonic sediments, western North America and eastern Europe: Geology, v. 4, p. 272-276.
Swindell, G.
S, 2002, Newark East Barnett Shale Walper, J. L., 1982, Plate tectonic evolution of the Fort Worth Basin, in Martin, C.A., ed., Petroleum geology of the Fort Worth basin and Bend arch area: Dallas Geological Society, p. 237-251. ACKNOWLEDGMENTSThe
authors are grateful for the constructive reviews of the manuscript by
Deborah Higley, Michael Brownfield, and William Keefer. We would also
like to thank Republic Energy, Inc. for permission to sample several of
their oil and |
Figure
1. Generalized diagram showing categories of conventional and continous
oil and 
Figure
2. Schematic plan view of a Total Petroleum System showing pod of
mature source rock, distribution of known petroleum occurrences, and
boundaries of the conventional- and continuous-type assessment units.
Figure
3. Map showing major structural elements (black lines), oil (green
dots) and 
Figure
4. Generalized stratigraphic subsurface section of USGS Bend Arch-Fort
Worth Basin Province showing stratigraphic extent of Barnett-Paleozoic
Total Petroleum System,
Figure
5. Events chart for Mississippian-Pennsylvanian Barnett-Paleozoic Total
Petroleum System (TPS)
Figure
6. (A) Location map and (B) generalized cross section AA’ of north Fort
Worth Basin area showing main 
Table 1. Plays identified in
the 1995 USGS National Oil and 